Transmission

ABSTRACT

An oil pan includes a lubricant guide surface positioned above a lower end of an output gear located at the lowest position in a gear train. The lubricant guide surface is inclined so as to descend toward the output gear in an axial view of the output gear, and is inclined so as to descend from opposite ends to a central part in the axial direction of the output gear on the lubricant guide surface.

TECHNICAL FIELD

The present invention relates to a transmission.

BACKGROUND ART

There is hitherto known a transmission (speed reducer) that reduces aspeed of an output of a driving source such as an electric motor via aplurality of gear trains.

CITATION LIST Patent Literature

[Patent Literature 1] Japanese Patent Laid-Open No. 2013-224710

SUMMARY OF INVENTION Technical Problem

In such a transmission as the above conventional one, it is common thata case supporting the gear train is filled with lubricant such asgrease, but when the flowability of the lubricant is low, the supply ofthe lubricant by spraying of the lubricant cannot be expected, making itdifficult to appropriately supply the lubricant to the entire geartrain.

The present invention was made in view of the circumstances describedabove, and an object of the present invention is to make it possible toappropriately supply lubricant to an entire gear train in a transmissionthat transmits power of a driving source.

Solution to Problem

This specification includes all contents of Japanese Patent ApplicationNo. 2016-229332 filed on Nov. 25, 2016.

For achieving the above object, in one aspect of the present invention,in a transmission including: a gear train driven by a driving source; acase that supports the gear train inside; lubricant with which the caseis filled; and an oil pan provided at a bottom of the case, the oil panincludes a lubricant guide surface positioned above a lower end of alowermost-level gear that is positioned at the lowest position in thegear train, and the lubricant guide surface is inclined so as to descendtoward the lowermost-level gear in an axial view of the lowermost-levelgear, and is inclined so as to descend from opposite ends to a centralpart in the axial direction of the lowermost-level gear on the lubricantguide surface.

With the configuration according to the one aspect of the presentinvention, the oil pan includes the lubricant guide surface positionedabove the lower end of the lowermost-level gear, and the lubricant guidesurface is inclined so as to descend toward the lowermost-level gear inthe axial view of the lowermost-level gear, and is inclined so as todescend from opposite ends to the central part in the axial direction ofthe lowermost-level gear on the lubricant guide surface. Accordingly, bythe lubricant guide surface that is inclined so as to descend toward thelowermost-level gear in the axial view of the lowermost-level gear andis inclined so as to descend from opposite ends toward the central part,the lubricant guided to the oil pan can be guided to the bottom of theoil pan in the vicinity of the lowermost-level gear. Hence the lubricantcirculating in the case can be once collected to the vicinity of thelowermost-level gear and efficiently circulated throughout the geartrain from the lowermost-level gear side, whereby the lubricant can beappropriately supplied to the entire gear train.

In one aspect of the present invention, the case includes a side wallfacing a tip of a driving source output shaft of the driving source, andthe side wall includes an inclined portion that is inclined so as to bemore separated in the axial direction from the driving source outputshaft toward the oil pan on a lower side.

With the configuration according to the one aspect of the presentinvention, it is possible to efficiently guide the lubricant in the caseto the oil pan on the lower side along the inclined portion of the sidewall.

Further, in one aspect of the present invention, the gear train includesa counter gear that meshes with the driving source output shaft, and thelowermost-level gear that meshes with the counter gear, the counter gearintegrally includes a driven gear portion that meshes with the drivingsource output shaft, and a driving gear portion that meshes with thelowermost-level gear, and at least a part of the driven gear portion ispositioned inside the oil pan.

With the configuration according to one aspect of the present invention,the counter gear integrally includes a driven gear portion that mesheswith the driving source output shaft, and a driving gear portion thatmeshes with the lowermost-level gear, and at least a part of the drivengear portion is positioned inside the oil pan. Hence the lubricant canbe supplied to the driving source output shaft by the driven gearportion, a part of which is positioned inside the oil pan to mesh withthe driving source output shaft. Further, the lubricant can be suppliedto the driving gear portion by the lowermost-level gear that meshes withthe driving gear portion.

Further, in one aspect of the present invention, a guide rib protrudingto an inside of the case is formed in the inclined portion, and theguide rib extends in an up-down direction.

With the configuration according to the one aspect of the presentinvention, since the guide rib formed in the inclined portion extends inthe up-down direction, it is possible to efficiently guide the lubricantto the oil pan on the lower side along the guide rib.

In one aspect of the present invention, the driving gear portion has adiameter smaller than that of the driven gear portion and is providedcloser to the side wall side than the driven gear portion.

With the configuration according to one aspect of the present invention,the guide rib can be compactly provided effectively using the space onthe driving gear portion having a diameter smaller than that of thedriven gear portion.

Further, in one aspect of the present invention, the guide rib isprovided above the driving gear portion, and overlaps with at least oneof the driven gear portion and a gear of the driving source output shaftin the axial view of the counter gear.

With the configuration according to one aspect of the present invention,the guide rib is provided above the driving gear portion, and overlapswith at least one of the driven gear portion and a gear of the drivingsource output shaft in the axial view of the counter gear. Hence theguide rib can be compactly provided by effectively using the space abovethe driving gear portion having a diameter smaller than that of thedriven gear portion. In addition, the lubricant from the driven gearportion and the gear of the driving source output shaft can beefficiently guided by the guide rib.

In one aspect of the present invention, the oil pan includes a lower endstorage that is depressed downward along the lower end of thelowermost-level gear to constitute a lower end of the oil pan.

With the configuration according to one aspect of the present invention,the lubricant can be collected to the lower end storage and effectivelycirculated, and the oil pan can be compactly formed in the peripheralportion of the lower end storage.

Further, in one aspect of the present invention, the lubricant guidesurface is inclined so as to descend toward the lower end storage.

With the configuration according to one aspect of the present invention,the lubricant guide surface is inclined so as to descend toward thelower end storage. With the lower end storage being the lower end of theoil pan, the lubricant can be easily collected and the lubricant can beefficiently supplied from the lower end storage to the gear train.

Further, in one aspect of the present invention, the lubricant guidesurface is provided below the inclined portion.

With the configuration according to one aspect of the present invention,since the lubricant guide surface is provided below the inclinedportion, the lubricant guided downward from the inclined portion can beefficiently guided to the lowermost-level gear side by the lubricantguide surface.

Advantageous Effects of Invention

In the transmission according to one aspect of the present invention, itis possible to appropriately supply lubricant to an entire gear train.

It is also possible to efficiently guide the lubricant to the oil pan onthe lower side along the inclined portion of the side wall.

It is also possible to appropriately supply the lubricant to the drivingsource output shaft and the driving gear portion.

It is also possible to efficiently guide the lubricant to the oil pan onthe lower side along the guide rib.

It is also possible to compactly provide the guide rib.

It is also possible to efficiently supply the lubricant from the lowerend storage of the oil pan to the gear train, and compactly form the oilpan.

It is also possible to efficiently guide the lubricant guided downwardfrom the inclined portion to the lowermost-level gear side with thelubricant guide surface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a left side view of a lawn mower according to an embodiment ofthe present invention.

FIG. 2 is a left side view of the rear of the lawn mower.

FIG. 3 is a perspective view of a transmission as viewed from the leftfront side.

FIG. 4 is a left side view of the transmission.

FIG. 5 is a sectional view taken along a line V-V of FIG. 4.

FIG. 6 is a sectional view taken along a line VI-VI of FIG. 4.

FIG. 7 is a sectional view of an oil pan taken along a plane vertical toan axial direction of a counter gear.

DESCRIPTION OF EMBODIMENT

Hereinafter, the embodiment of the present invention will be describedwith reference to the drawings. During the description, directions suchas front-rear, right-left, and up-down will be described taking aforward direction of a lawn mower 1 (work machine) as the front of themachine body. Symbol FR indicated in each drawing denotes the front ofthe machine body, symbol UP denotes the upper part of the machine body,and symbol LH denotes the left of the machine body.

FIG. 1 is a left side view of the lawn mower 1 according to theembodiment of the present invention. FIG. 2 is a left side view of therear of the lawn mower 1. In FIGS. 1 and 2, as for ones provided as alateral pair, only the left-side one is illustrated including itsnumeral. In addition, in FIG. 2, a part of the machine body is omittedfor illustrating the internal configuration of the rear of the lawnmower 1.

The lawn mower 1 is a walking type self-propelled work machine withwhich an operator walks while operating the self-propelled lawn mower 1.

The lawn mower 1 includes: a housing 10; a lateral pair of front wheels11, 11 provided on the right and left of the front of the housing 10; alateral pair of rear wheels 12, 12 provided on the right and left of therear of the housing 10; a lawn mowing cutter blade 13 housed inside thehousing 10; and a driving motor (not illustrated) as a power source todrive the cutter blade 13. The driving motor is supported by the housing10. Note that the power source of the cutter blade 13 may be an engine.

Further, the lawn mower 1 includes; an electric motor 14 (drivingsource) as a travelling power source to drive the rear wheels 12, 12; atransmission 15 that transmits the power of the electric motor 14 toeach of the rear wheels 12, 12; a box-shaped mown grass container 16attached to the rear of the housing 10; an operation handle 17 extendingrearward and upward from the rear of the housing 10. The upper end ofthe operation handle 17 is provided with an operation unit 17 a for theoperator to control the number of revolutions of the driving motor, thenumber of revolutions of the electric motor 14, and the like. Thetransmission 15 is provided in the rear of the housing 10.

The electric motor 14 is driven by a battery mounted in the lawn mower1. The lawn mower 1 moves forward by rotation of the rear wheels 12, 12that are driven by the electric motor 14. As the driving source, anengine (internal combustion engine) may be used in place of the electricmotor 14.

The housing 10 is formed in the shape of a case with its lower surfaceopen, the lower surface facing a lawn, and the cutter blade 13 faces thelawn from the open portion on the lower surface of the housing 10. Thecutter blade 13 is fixed to the lower end of a rotation shaft 18extending in the up-down direction inside the housing 10, and mows glassby rotating around the rotation shaft 18 driven by the driving motor.The glass mown with the cutter blade 13 is called “mown glass.” The mownglass is discharged rearward through a path in the housing 10 and housedinto the mown grass container 16.

FIG. 3 is a perspective view of the transmission 15 as viewed from theleft front side. FIG. 4 is a left side view of the transmission 15. FIG.5 is a sectional view taken along a line V-V of FIG. 4.

With reference to FIGS. 3 to 5, the transmission 15 includes: an inputshaft 20 into which the power from the electric motor 14 is input; atransmission shaft 21 that meshes with the input shaft 20; and an outputshaft 22 that meshes with the transmission shaft 21. The input shaft 20,the transmission shaft 21, and the output shaft 22 extend parallel toone another in a machine-width direction of the lawn mower 1.

Further, the transmission 15 includes an input shaft 20, a case 23 thathouses the transmission shaft 21 and the output shaft 22; an adapter 24interposed between the case 23 and the electric motor 14, and a covermember 25 that covers the electric motor 14.

The transmission 15 is a speed reducer that reduces the speed ofrotation, input from the electric motor 14, and outputs the rotationfrom the output shaft 22.

The electric motor 14 includes a cylindrical motor body portion 14 ahaving a rotor and the like provided inside, and a motor output shaft 14b (driving source output shaft) extending from the central part of themotor body portion 14 a.

The input shaft 20 includes a motor output shaft 14 b, and an input gear26 (a gear of the driving source output shaft) fixed to the motor outputshaft 14 b.

The transmission shaft 21 includes a shaft 27 supported by the case 23,and a counter gear 28 (gear) that meshes with the input gear 26 and isrotatable on the shaft 27.

The output shaft 22 includes an axle 29 supported by the case 23, and anoutput gear 30 (lowermost-level gear) that meshes with the counter gear28 of the transmission shaft 21 and is integrally fixed with the axle29.

The axle 29 is provided penetrating the case 23 of the lawn mower 1 inthe machine-width direction. That is, the transmission 15 is mounted inthe lawn mower 1 with the axle 29 extending in the machine-widthdirection. The right and left rear wheels 12, 12 (FIG. 1) arerespectively provided at the right and left ends of the axle 29.Specifically, the transmission 15 is disposed to be offset on one side(left side) with respect to the center of the machine width of the lawnmower 1. Hence an amount of the axle 29 extended from the transmission15 is smaller on the left side than on the right side.

The electric motor 14 is fixed to the right side surface of the case 23via the adapter 24. In other words, the electric motor 14 is fixed tothe inner side surface of the case 23 in the machine-width direction.

The case 23 includes, a case body 31 that houses a gear train 19 made upof the input gear 26, the counter gear 28, and the output gear 30, andan oil pan 32 provided at the bottom of the case body 31.

The case body 31 includes a one-side side wall 33 through which themotor output shaft 14 b of the electric motor 14 is inserted from theoutside, the other-side side wall 34 (side wall) facing the one-sideside wall 33, a wall 35 constituting the front surface, the uppersurface, and the rear surface of the case body 31, and the lower-surfaceopening 36 that opens downward the internal space of the case body 31.The lower-surface opening 36 is blocked by the oil pan 32.

As illustrated in FIG. 5, an insertion hole 37, through which theone-side side wall 33 penetrates, is formed in the one-side side wall 33in the upper part of the case body 31, and the motor output shaft 14 bconstituting the input shaft 20 is inserted through the insertion hole37 from the outside.

The transmission shaft 21 is supported by a shaft support portion 38disposed immediately below the input shaft 20 and formed in the casebody 31. The shaft support portion 38 includes a one-side support holeportion 39 (support hole portion) provided in the one-side side wall 33,and the other-side support hole portion 40 provided in the other-sideside wall 34 in a concentric positional relation with the one-sidesupport hole portion 39.

The one-side support hole portion 39 is a through hole penetrating theone-side side wall 33 in the machine-width direction, and is formed withan opening 39 a that communicates the space in the case body 31 to theoutside. The other-side support hole portion 40 is a blind hole formedin the inner surface of the other-side side wall 34, and does notpenetrate the other-side side wall 34.

The shaft 27 of the transmission shaft 21 is fixed to the case body 31by fitting of one end 27 a (one end of the transmission shaft and oneend of the shaft) into the one-side support hole portion 39 and byfitting of the other end 27 b into the other-side support hole portion40.

The one end 27 a of the shaft 27 is formed with a protrusion 27 cprotruding from the opening 39 a of the one-side support hole portion 39to the outside of the one-side side wall 33.

Further, a seal member 41 is provided between the outer periphery of theone end 27 a and the inner periphery of the one-side support holeportion 39. The seal member 41 is an O-ring made of rubber, for example,and fitted into an annular groove formed in the outer periphery of theone end 27 a.

The counter gear 28 of the transmission shaft 21 is rotatably providedon the shaft 27 by engagement of a hole portion, provided at the centerof the counter gear 28, with the outer periphery of the portion betweenthe one end 27 a and the other end 27 b of the shaft 27.

The counter gear 28 has a driven gear portion 28 a that meshes with theinput gear 26, and a driving gear portion 28 b that meshes with theoutput gear 30. The driven gear portion 28 a and the driving gearportion 28 b are integrally formed while arranged in the axial directionof the shaft 27, the driven gear portion 28 a is positioned on theone-side side wall 33 side and the driving gear portion 28 b ispositioned on the other-side side wall 34 side. The driving gear portion28 b is a gear having a diameter smaller than that of the driven gearportion 28 a.

The output shaft 22 is disposed below the transmission shaft 21 and in aposition offset in the front-rear direction (rear) with respect to thetransmission shaft 21.

The case body 31 includes an axle support hole portion 43 penetratingthe one-side side wall 33, and an axle support hole portion 44 providedconcentrically with the axle support hole portion 43 and penetrating theother-side side wall 34.

The axle 29 of the output shaft 22 is inserted into the axle supporthole portions 43, 44 to be pivotally supported by the axle support holeportion 43 and the axle support hole portion 44. Specifically, the axle29 is supported via cylindrical bushes 45, 45 fitted to the innerperipheries of the axle support hole portions 43, 44. In addition,annular oil seals 46, 46, which seal between the axle 29 and the axlesupport hole portions 43, 44, are provided outside the bushes 45, 45 inthe axial direction in the axle support hole portions 43, 44.

The output gear 30 is fixed to the axle 29 with a pin 47 that isprovided so as to penetrate the output gear 30 and the axle 29 in aradial direction. The output gear 30 is a gear having a diameter largerthan that of the driving gear portion 28 b of the counter gear 28.

FIG. 6 is a sectional view taken along a line VI-VI of FIG. 4.

With reference to FIGS. 4 to 6, the adapter 24 includes the platyportion 50 formed in a circular plate shape, a tubular portion 51protruding in a plate thickness direction from the central part of theplaty portion 50, a fixing portion 52 provided on the outer periphery ofthe platy portion 50, a cover fixing portion 53 to which the covermember 25 is fixed, and a motor fixing portion 54.

The platy portion 50 includes a case contact surface 50 a in contactwith the outer surface of the one-side side wall 33 of the case body 31,and a motor attachment surface 50 b to which the motor body portion 14 ais attached on the rear surface side of the case contact surface 50 a.The case contact surface 50 a is formed with a contact portion 50 c(FIG. 5) in contact with the one end 27 a of the shaft 27.

The adapter 24 is made of a material having electric insulation and ismade of resin, ceramics, or the like.

A fixing portion 52 is a hole for insertion of an adapter fixing bolt 55that fixes the adapter 24 to the case body 31. A plurality of fixingportions 52 are provided at substantially equal intervals in acircumferential direction of the platy portion 50.

A plurality of cover fixing portions 53 are provided at substantiallyequal intervals in the circumferential direction of the platy portion50.

The motor fixing portion 54 is a hole portion for fastening of a motorfixing bolt 56 (FIG. 6) that fastens the motor body portion 14 a to theadapter 24. A plurality of motor fixing portions 54 are provided atsubstantially equal intervals in the circumferential direction of theplaty portion 50. Each of the motor fixing portions 54 is provided at aposition more inside than the fixing portion 52 and the cover fixingportion 53 in the radial direction of the platy portion 50.

The adapter 24 is disposed such that the case contact surface 50 a comesinto contact with the one-side side wall 33 while a tubular portion 51is fitted into the insertion hole 37 of the one-side side wall 33, andthe adapter 24 is fastened to one-side side wall 33 with the adapterfixing bolt 55 that is inserted into each fixing portion 52 from themotor attachment surface 50 b side.

The electric motor 14 is disposed such that the motor output shaft 14 bis inserted into the tubular portion 51 of the adapter 24 and the endsurface of the motor body portion 14 a comes into contact with the motorattachment surface 50 b of the adapter 24. The electric motor 14 isfastened to the motor fixing portion 54 with a motor fixing bolt 56 thatis inserted through a flange portion 14 c on the outer periphery of themotor body portion 14 a.

As thus described, by attaching the electric motor 14 to the insulatingadapter 24, the electric motor 14 can be fixed to the transmission 15while being electrically insulated from the case 23.

As illustrated in FIG. 5, in the state where the adapter 24 has beenattached to the case body 31, the contact portion 50 c of the adapter 24comes into contact with the protrusion 27 c of the one end 27 a of theshaft 27 protruding to the outside through the opening 39 a, and pressesthe shaft 27 to the other-side support hole portion 40 side in the axialdirection. That is, the shaft 27 of the transmission shaft 21 isretained with respect to the shaft support portion 38 by the contactportion 50 c of the adapter 24.

Specifically, the contact portion 50 c is a recess formed by recessingof the case contact surface 50 a in the protruding direction of theprotrusion 27 c, and the protrusion 27 c comes into contact with thebottom of the recess.

As thus described, the shaft 27 can be retained by the adapter 24configured to fix the electric motor 14 in the insulated state to thetransmission 15, so that it is possible to omit a dedicated retainingmember and simplify the structure of the transmission 15.

With the one-side support hole portion 39 including the opening 39 a,one end 27 a of the shaft 27 and the contact portion 50 c can be easilybrought into contact with each other through the opening 39 a.

Further, in the transmission shaft 21, the counter gear 28 rotates onthe shaft 27 and the shaft 27 hardly rotates, so that the shaft 27 canbe retained even in the configuration where the adapter 24 is broughtinto contact with the one end 27 a of the shaft 27.

Moreover, with the seal member 41 provided between the one end 27 a ofthe shaft 27 and the one-side support hole portion 39, the sealabilityof the case body 31 can be ensured even in the configuration where theone-side support hole portion 39 includes the opening 39 a.

The cover member 25 integrally includes a tubular peripheral wall 25 athat covers the outer periphery of the motor body portion 14 a, and aside wall 25 b that closes one end of the peripheral wall 25 a to coverthe end surface of the motor body portion 14 a in the axial direction.In the peripheral wall 25 a and the side wall 25 b, a plurality of airvents 25 c are formed.

The peripheral wall 25 a includes an engagement piece 25 d protruding tothe adapter 24 side from the end opposite from the side wall 25 b. Theengagement piece 25 d includes a protrusion 25 e protruding from theouter periphery of the tip to the outside of the peripheral wall 25 a inthe radial direction in a fingernail shape. A plurality of engagementpieces 25 d are formed at substantially equal intervals in thecircumferential direction of the peripheral wall 25 a.

The cover fixing portion 53 of the adapter 24 is a hole portion intowhich the engagement piece 25 d of the cover member 25 is inserted. Thecover member 25 is fixed to the adapter 24 by insertion and engagementof each engagement piece 25 d into each cover fixing portion 53.

The case 23 is filled with lubricant (not illustrated) that makes theinput shaft 20, the transmission shaft 21, and the output shaft 22lubricant. The lubricant is grease in the present embodiment, but thelubricant may be oil. The lubricant is stored in the lower part of thecase 23 including the oil pan 32.

In the case 23, the input gear 26, the counter gear 28, and the outputgear 30 are arranged sequentially from above in the up-down direction.

As illustrated in FIG. 4, the lower parts of the counter gear 28 and theoutput gear 30 are positioned inside the oil pan 32.

In the counter gear 28 and the output gear 30, at least the lower ends28 c, 30 a are positioned inside the oil pan 32 and in contact with thelubricant stored in the oil pan 32. For this reason, in a state wherethe transmission 15 is driven by the electric motor 14, the lubricant ofthe oil pan 32, which adheres to each of the counter gear 28 and theoutput gear 30, is supplied upward by centrifugal force of the rotationof each of the counter gear 28 and the output gear 30, and is alsosupplied to a gear that directly meshes with the counter gear 28 and theoutput gear 30.

Specifically, as illustrated in FIG. 4, the output gear 30 meshes withthe gear portion 28 b of the counter gear 28, thereby enabling adhesionof the lubricant of the oil pan 32 to the driving gear portion 28 b viathe output gear 30. It is thus possible to appropriately supply thelubricant to the driving gear portion 28 b positioned above the oil pan32.

Further, as illustrated in FIG. 4, the driven gear portion 28 a of thecounter gear 28 has its lower end 28 c positioned inside the oil pan 32and meshes with the input gear 26 of the electric motor 14. This enablesadhesion of the lubricant of the oil pan 32 to the input gear 26 via thedriven gear portion 28 a. It is thus possible to appropriately supplythe lubricant to the input gear 26 positioned above the oil pan 32.

A part of the lubricant, supplied from the oil pan 32 to the input gear26, the counter gear 28, and the output gear 30, drops by gravity toreturn to the oil pan 32 and is supplied again from the oil pan 32 toeach of the input gear 26, the counter gear 28, and the output gear 30.

With reference to FIGS. 3 to 5, the other-side side wall 34 facing thetip of the motor output shaft 14 b includes in its upper part aperpendicular portion 34 a facing the tip of the motor output shaft 14b, and an inclined portion 34 b inclined from the lower end of theperpendicular portion 34 a and extending downward.

The inclined portion 34 b is inclined so as to be more separated in theaxial direction from the motor output shaft 14 b toward the lower oilpan 32 side. The inclined portion 34 b is provided immediately above thegear portion 28 b of the counter gear 28, and formed in a positionoverlapping with the side surface of the upper part of the driven gearportion 28 a in the axial view of the driven gear portion 28 a asillustrated in FIG. 4. The interval between the inclined portion 34 band the side surface of the driven gear portion 28 a increases in thedownward direction.

The inclined portion 34 b includes, on its inner surface, guide ribs 60,60 protruding to the inside of the case 23. A pair of guide ribs 60, 60are provided substantially parallel to an imaginary line S connectingthe center of the input gear 26 and the center of the counter gear 28,and extend in the up-down direction. As illustrated in FIG. 4, the pairof guide ribs 60, 60 are provided so as sandwich the line S fromopposite sides in the axial view of the counter gear 28, and arearranged in the front and rear of the counter gear 28.

The guide ribs 60, 60 are provided below the input gear 26 and above thedriving gear portion 28 b, and are formed in positions overlapping withthe side surface of the upper part of the driven gear portion 28 a inthe axial view of the counter gear 28 (FIG. 4).

FIG. 7 is a sectional view of the oil pan 32 taken along a planevertical to the axial direction of the counter gear 28. In FIG. 7, thegear train 19 is illustrated together with the oil pan 32.

With reference to FIGS. 3 to 5, and 7, the oil pan 32 includes apot-like storage 61 with its upper surface open, and a flange portion 62extending from the upper edge of the storage 61 to the lateral outside.The oil pan 32 is fixed to the lower surface of the case body 31 with aplurality of oil pan fixing bolts 63 inserted into the flange portion 62from below.

The storage 61 includes a lower end storage 65 and a lubricantintroduction portion 66 formed above the lower end storage 65, the lowerend storage 65 covering from below the output gear 30 that is thelowermost-level gear located at the lowest position in the gear train19.

The lubricant introduction portion 66 is positioned immediately belowthe counter gear 28 and covers the counter gear 28 from below.

The lower end storage 65 constitutes the lower end of the oil pan 32that is depressed downward along the lower end 30 a of the output gear30.

The bottom of the lubricant introduction portion 66 is formed by alubricant guide surface 67 that is inclined so as to descend toward thelower end storage 65.

Specifically, as illustrated in FIG. 7, in the axial view of the outputgear 30, the lubricant guide surface 67 is inclined so as to descendtoward the output gear 30 from an upper end 67 a, which is positioned onthe opposite side from the lower end storage 65, to a lower end 67 b.Further, as illustrated in FIG. 5, the lubricant guide surface 67 isinclined so as to descend from opposite ends 67 c, 67 c of the outputgear 30 in the axial direction on the lubricant guide surface 67 towarda central part 67 d of the output gear 30 in the axial direction on thelubricant guide surface 67. A valley shape going downward from oppositeends 67 c, 67 c toward the central part 67 d is formed in the range fromthe upper end 67 a to the lower end 67 b. That is, the lubricant guidesurface 67 is formed in a tub shape declining toward the output gear 30and depressed such that the central part 67 d in the width direction isthe lowest.

With reference to FIGS. 4 and 5, when a part of lubricant L, suppliedfrom the oil pan 32 to each of the input gear 26 and the counter gear28, drops and returns to the oil pan 32 as illustrated in FIGS. 4 and 5,the part of the lubricant L moves downward along the inner surface ofthe inclined portion 34 b positioned below the input gear 26. In thepresent embodiment, since the internal space of the case 23 is wider onthe lower side due to the inclined portion 34 b, it is possible toefficiently guide the lubricant in the upper part of the case 23 to theoil pan 32 on the lower side.

Further, since the guide ribs 60, 60 extending in the up-down directionare formed in the inclined portion 34 b, the rigidity of the other-sideside wall 34 can be improved by the guide ribs 60, 60, and the lubricantcan be efficiently guided by the guide ribs 60, 60 to the oil pan 32 onthe lower side

The lubricant having moved from the inclined portion 34 b to thelubricant guide surface 67 immediately below the inclined portion 34 bmoves downward to the output gear 30 side along the lubricant guidesurface 67 that declines toward the lower end storage 65, and reachesthe lower end storage 65. In the present embodiment, the lubricant guidesurface 67 is inclined so as to descend from opposite ends 67 c, 67 c ofthe output gear 30 in the axial direction on the lubricant guide surface67 toward the central part 67 d, whereby the lubricant can be collectedto the central part 67 d and the flow of the lubricant moving downwardtoward the lower end storage 65 can be formed easily. It is therebypossible to efficiently return the lubricant to the lower end storage 65and efficiently circulate the lubricant from the lower end storage 65 tothe gear train 19.

As described above, according to the embodiment to which the presentinvention has been applied, the transmission 15 includes: thetransmission shaft 21 driven by the electric motor 14; and the case 23that supports the electric motor 14 and the transmission shaft 21, thetransmission including the adapter 24 which is interposed between thecase 23 and the electric motor 14 and to which the electric motor 14 isattached, and the adapter 24 is in contact with one end 27 a of thetransmission shaft 21 in the axial direction of the transmission shaft21. As a result, the transmission shaft 21 can be retained using theadapter 24 to which the electric motor 14 is attached, so that it ispossible to omit a dedicated retaining member and simplify the structureof the transmission 15.

Further, since the adapter 24 is made of a material having electricinsulation, it is possible to attach the electric motor 14 to thetransmission 15 in an electrically insulated state, and retain thetransmission shaft 21 by using the adapter 24.

Moreover, the case 23 includes the opening 39 a that exposes the one end27 a of the transmission shaft 21 to the outside of the case 23, and theone end 27 a of the transmission shaft 21 and the adapter 24 are incontact with each other in the axial direction of the transmission shaft21 through the opening 39 a. It is thus possible to bring the adapter 24into contact with the one end 27 a of the transmission shaft 21 exposedfrom the opening 39 a and retain the transmission shaft 21 with a simplestructure.

The transmission shaft 21 includes the shaft 27 supported by the case23, and the counter gear 28 rotationally provided on the shaft 27 tomesh with the motor output shaft 14 b of the electric motor 14, and theshaft 27 is retained by the adapter 24. As a result, the shaft 27supporting the counter gear 28 hardly rotates, so that the shaft 27 canbe easily retained by the adapter 24.

Further, the case 23 includes the one-side support hole portion 39 thatsupports the one end 27 a of the shaft 27 and communicates with theinside and the outside of the case 23, the one end 27 a and the adapter24 are in contact with each other in the axial direction of the shaft 27through the support hole portion 39, and the seal member 41 is providedbetween the outer periphery of the one end 27 a and the support holeportion 39. Hence the one end 27 a of the shaft 27 and the adapter 24can be brought into contact with each other through the one-side supporthole portion 39 of the case 23 to retain the shaft 27 with a simplestructure, and the case 23 can be favorably sealed by the seal member 41provided between the outer periphery of the one end 27 a and the supporthole portion 39.

Moreover, since the cover member 25 covering the electric motor 14 isattached to the adapter 24, it is possible to attach the cover member 25with a simple structure.

According to the embodiment to which the present invention has beenapplied, the transmission 15 includes: the gear train 19 driven by theelectric motor 14; the case 23 that supports the gear train 19 inside;the lubricant that fills the case 23; and the oil pan 32 provided at thebottom of the case 23, the oil pan 32 includes the lubricant guidesurface 67 that is positioned above the lower end 30 a of the outputgear 30 located at the lowest position in the gear train 19, and thelubricant guide surface 67 is inclined so as to descend toward theoutput gear 30 in the axial view of the output gear 30, and is inclinedso as to descend from opposite ends 67 c, 67 c of the output gear 30 inthe axial direction on the lubricant guide surface 67 toward the centralpart 67 d. Accordingly, by the lubricant guide surface 67 that isinclined so as to descend toward the output gear 30 in the axial view ofthe output gear 30 and is inclined so as to descend from opposite ends67 c, 67 c toward the central part 67 d, the lubricant guided to the oilpan 32 can be guided to the bottom of the oil pan 32 in the vicinity ofthe output gear 30. Hence the lubricant circulating in the case 23 canbe once collected to the vicinity of the output gear 30 and efficientlycirculated throughout the gear train 19 from the output gear 30 side,and the lubricant can be appropriately supplied to the entire gear train19.

The case 23 includes the other-side side wall 34 facing the tip of themotor output shaft 14 b of the electric motor 14, and the other-sideside wall 34 includes the inclined portion 34 b that is inclined so asto be more separated from the motor output shaft 14 b in the axialdirection toward the lower oil pan 32 side. Accordingly, it is possibleto efficiently guide the lubricant in the case 23 to the oil pan 32 onthe lower side along the inclined portion 34 b of the other-side sidewall 34.

The gear train 19 includes the counter gear 28 that meshes with themotor output shaft 14 b and the output gear 30 that meshes with thecounter gear 28, the counter gear 28 integrally includes the driven gearportion 28 a that meshes with the motor output shaft 14 b and thedriving gear portion 28 b that meshes with the output gear 30, and inthe driven gear portion 28 a, at least the lower end 28 c is positionedinside the oil pan 32. Hence the lubricant can be supplied to the motoroutput shaft 14 b by the driven gear portion 28 a that has its lower end28 c positioned inside the oil pan 32 and meshes with the motor outputshaft 14 b. Further, the lubricant can be supplied to the driving gearportion 28 b by the output gear 30 that meshes with the driving gearportion 28 b provided inside the oil pan 32.

The guide ribs 60, 60 protruding to the inside of the case 23 are formedin the inclined portion 34 b, and the guide ribs 60, 60 are extended inthe up-down direction, whereby it is possible to efficiently guide thelubricant to the oil pan 32 on the lower side along the guide ribs 60,60.

The driving gear portion 28 b has a diameter smaller than that of thedriven gear portion 28 a and is provided closer to the other-side sidewall 34 side than the driven gear portion 28 a. Hence the guide ribs 60,60 can be compactly provided effectively using the space on the drivinggear portion 28 b having a diameter smaller than that of the driven gearportion 28 a.

The guide ribs 60, 60 are provided above the driving gear portion 28 b,and overlap with the driven gear portion 28 a in the axial view of thecounter gear 28. Hence the guide ribs 60, 60 can be compactly providedeffectively using the space above the driving gear portion 28 b having adiameter smaller than that of the driven gear portion 28 a. Further, thelubricant from the driven gear portion 28 a can be efficiently guided bythe guide ribs 60, 60.

The oil pan 32 includes the lower end storage 65 constituting the lowerend of the oil pan 32 that is depressed downward along the lower end 30a of the output gear 30. Accordingly, the lubricant can be collected tothe lower end storage 65 and effectively circulated, and the oil pan 32can be compactly formed in the peripheral portion of the lower endstorage 65.

The lubricant guide surface 67 is inclined so as to descend toward thelower end storage 65. With the lower end storage 65 being the lower endof the oil pan 32, the lubricant can be easily collected and thelubricant can be efficiently supplied from the lower end storage 65 tothe gear train 19.

Further, with the lubricant guide surface 67 being provided below theinclined portion 34 b, the lubricant guided downward from the inclinedportion 34 b can be efficiently guided to the lowermost-level gear sideby the lubricant guide surface 67.

Note that the above embodiment illustrates one aspect to which thepresent invention has been applied, but the present invention is notlimited to the above embodiment.

In the above embodiment, the description has been given assuming thatthe contact portion 50 c that is the recessed portion of the adapter 24comes into contact with the one end 27 a of the shaft 27 protrudingoutside through the opening 39 a, but the present invention is notlimited thereto, and the contact portion 50 c may only have a shapecapable of retaining the shaft 27. For example, the one end 27 a of theshaft 27 may be formed to be flush with the outer end of the opening 39a and the flat contact portion of the adapter 24 may be brought intocontact with the one end 27 a. Alternatively, in order for the one end27 a to be positioned more inside than the outer end of the opening 39a, the shaft 27 may be formed shorter than the state of FIG. 5, aprotruding contact portion that protrudes to the inside of the opening39 a may be formed in the adapter 24, and the contact portion may bebrought into contact with the one end 27 a. The contact portion 50 c maynot necessarily be in constant contact with the one end 27 a, but may beconfigured to come into contact with the one end 27 a at the time ofmovement of the shaft 27.

Further, the contact portion 50 c may come into contact with the shaft27 via the spacer that is interposed between the contact portion 50 cand the one end 27 a.

In the above embodiment, the description has been given assuming thatthe contact portion 50 c that is the recessed portion of the adapter 24comes into contact with the one end 27 a of the shaft 27, but a gap maybe formed between the one end 27 a and the contact portion 50 c as longas the shaft 27 can be retained by the adapter 24. In this instance, byshifting the shaft 27 to the contact portion 50 c side in the axialdirection, the one end 27 a comes into contact with the contact portion50 c, and the shaft 27 is retained.

In the above embodiment, the description has been given assuming thatthe guide ribs 60, 60 overlap with the driven gear portion 28 a in theaxial view of the counter gear 28, but this is not restrictive, and theguide ribs 60, 60 can be configured so as to overlap with at leasteither the driven gear portion 28 a or the input gear 26 of the motoroutput shaft 14 b in the axial view of the counter gear 28. For example,in FIG. 4, when the guide ribs 60, 60 are disposed closer to theimaginary line S, the guide ribs 60, 60 can overlap with both the drivengear portion 28 a and the input gear 26 in the axial view of the countergear 28.

REFERENCE SIGNS LIST

-   14 Electric motor (Driving source)-   14 b Motor output shaft (Driving source output shaft)-   15 Transmission-   19 Gear train-   23 Case-   26 Input gear (Gear of driving source output shaft)-   28 Counter gear-   28 a Driven gear portion-   28 b Driving gear portion-   28 c Lower end (Part)-   34 Output gear (Lowermost-level gear)-   30 a Lower end-   32 Oil pan-   34 Other-side side wall (Side wall)-   34 b Inclined portion-   60, 60 Guide rib-   65 Lower end storage-   67 Lubricant guide surface-   67 c, 67 c Opposite ends-   67 d Central part

The invention claimed is:
 1. A transmission comprising: a gear traindriven by a driving source; a case that supports the gear train inside;an oil pan provided at a bottom of the case; lubricant stored in a lowerpart of the case, said lower part of the case including the oil pan,wherein the oil pan includes a lubricant guide surface positioned abovea lower end of a lowermost-level gear, said lowermost-level gear havingan axis and being positioned at a lowest position in the gear train, andthe lubricant guide surface is inclined so as to descend toward thelowermost-level gear, when viewed in the axis of the lowermost-levelgear, and the lubricant guide surface includes a portion facing thelowermost-level gear from a lower side of the lowermost-level gear, thelubricant guide surface portion includes opposite ends, which arelocated at both ends of the lubricant guide surface in an axialdirection of the lowermost-level gear, and a central part, which islocated at a center of the lubricant guide surface in the axialdirection of the lowermost-level gear, and the lubricant guide surfaceis inclined in the axial direction of the lowermost-level gear so as todescend from the opposite ends to the central part of thelowermost-level gear, wherein the central part is a lowest part of thelubricant guide surface in the axial direction, the driving source has adriving source output shaft; the case includes a side wall facing a tipof the driving source output shaft, the side wall includes an inclinedportion that is inclined in the axial direction relative to the drivingsource output shaft so as to be simultaneously inclined toward the oilpan and away from the driving source output shaft, the gear train ispositioned below the driving source output shaft and includes a countergear that meshes with the driving source output shaft, and thelowermost-level gear meshes with the counter gear, the side wallincludes a support hole portion supporting an end portion, in the axialdirection, of the counter gear, the inclined portion connects a portionof the side wall to the support hole portion, the portion of thesidewall faces the tip of the driving source output shaft, the countergear includes a driven gear portion and a driving gear portion, thedriven gear portion meshes with the driving source output shaft and thedriving gear portion meshes with the lowermost-level gear, the drivinggear portion has a diameter smaller than that of the driven gear portionand is provided closer to the side wall side than the driven gearportion, a guide rib protruding to an inside of the case is formed inthe inclined portion, the guide rib extends in an up-down direction, andthe guide rib is provided above the driving gear portion, and overlapswith the driven gear portion in the axial view of the counter gear. 2.The transmission according to claim 1, wherein the counter gearintegrally includes the driven gear portion that meshes with the drivingsource output shaft, and the driving gear portion that meshes with thelowermost-level gear, and at least a part of the driven gear portion ispositioned inside the oil pan.
 3. The transmission according to claim 1,wherein the oil pan includes a lower end storage that is depresseddownward along the lower end of the lowermost-level gear to constitute alower end of the oil pan.
 4. The transmission according to claim 3,wherein the lubricant guide surface is inclined so as to descend towardthe lower end storage.
 5. The transmission according to claim 1, whereinthe lubricant guide surface is provided below the inclined portion.